US Congress(CHICAGO) -- Former Illinois congressman Jesse Jackson Jr. has reached a plea agreement in connection to a federal probe into whether or not the troubled lawmaker misused campaign funds.

Earlier this month Jackson pleaded guilty to one count of conspiracy to commit wire fraud, mail fraud and making false statements, sources close to the investigation told ABC's Chicago television affiliate WLS. Jackson could now face up to five years in jail, a decision that will ultimately be made by a federal judge. The former congressman signed the plea deal on Feb. 1 in the nation's capital.

The U.S. Attorney's Office in Washington, D.C., which has been running this investigation, had no comment when contacted Friday by ABC News.

The plea agreement comes a little over two months after Jackson stepped down from Congress. In his resignation letter to House Speaker John Boehner, Jackson, D-Ill., acknowledged that he had made his "share of mistakes."

"I am aware of the ongoing federal investigation into my activities and I am doing my best to address the situation responsibly, cooperate with the investigators, and accept responsibility for my mistakes, for they are my mistakes and mine alone," he wrote in the letter. "None of us is immune from our share of shortcomings or human frailties and I pray that I will be remembered for what I did right."

For months leading up to his resignation, Jackson had been on medical leave undergoing treatment for bipolar disorder. Last June, Jackson, the son of civil rights leader Jesse Jackson, suddenly left Congress to seek treatment for "exhaustion," according to his office. Weeks later his staff noted that his condition was "more serious" than initially thought. Jackson went on to spend time at treatment centers in Arizona and Minnesota before being diagnosed with bipolar disorder.

Despite his troubles, Jackson, whose district included a large portion of Chicago's South Side and southeast suburbs, still won re-election in a landslide last November. But shortly afterward, he resigned.

"Against the recommendations of my doctors, I had hoped and tried to return to Washington and continue working on the issues that matter most to the people of the Second District. I know now that will not be possible," Jackson wrote in his letter. "The constituents of the Second District deserve a full-time legislator in Washington, something I cannot be for the foreseeable future. My health issues and treatment regimen have become incompatible with service in the House of Representatives."

According to reports, Jackson will now repay the government hundreds of thousands of dollars that he used to buy items such as a $40,000 luxury watch and home furniture.

His wife, Sandi Jackson, is also the subject of a federal probe. She left her spot on the Chicago City Council last month.